Process of treating oil and gas wells to increase production



l66-3075 XR 2265923 5R D 1 1- J. s. 'N'ORMAND 2,265,923

PROCESS 9F TREATING OII=-AND G AS WELLS To INCREASE PRODUCTION Fied-Nov. '17, 1958 R I swam Eton v v E (IQ-$6,871. Normano l,

part ofFig. 1, showing the-effect oi the processes heretofore used.

In the treatment of 'oil or gas wells to :augment their flow, inaccordance with my invention, the

"cate would be effective to produce the solvent or chemical actiondesired. Many such'l-i-quids have been used advantageouslyin welltreatment, and

for the purposes of this specification, I hove adopted and use the term"treatment liquid to indicate any substance or solution or mixturethereof which is liquid under normal temperatures at atmosphericpressure and capable of dissolving paraffin or asphalt, such ascarbon-tetrachloride or hydrocarbon compounds and mixtures thereof suchas benz-ine, naphtha, 01' cos-- inghead gasoline, and likewise to meanany substance or solution or mixture of substances which is liquid undernormal temperatures at atmospheric pressure and capable of reactingchemically with any constituent of the producing for mation to formreaction products which may be removed from the well.

Generally stated, my invention comprises the treatment of a wellbypreheating the producing formation adjacent the well bore, applying apressure sui'l'lciently in excess of the reel: pressure to force thefluid from the bottom of the well bore back into the producing formationarray from the well bore and, while maintaining such pressure,introducing into the top of'the Well av hot compressed gaseous mediumcontaining the treatment liquid in the form of vapor, .the ten 1--perature of such gaseous medium and the fac'e of the producingformat-ion, as well as the parts with which it contacts on the waythereto, being maintained in excess of the temperature of cone densatlonoi the treatment liquid at the exi'sting pressure.

' In ecidizing a well, it is essential that the bot tom of the Well borebe clean, so that the acid can reach the producingformntion, and toprevent the generation by the action of the acid upon the sediment andother substances, of a gelatinous mass of inuck which i extremely'difiicult to remove and greatly retards the flow. While the-process oi'acidizi-ng in socordun'ce with my invention can be appliedtowellsclenned lay-other methods, or to such new wells as do not requirecleaning, the cleaning and the scidizing in accordance with my inventionare carried out genorally in the same manner, by the some apparatus, andpreferably as a series of consecutive and similar-steps, and if awell'is to be a'cidizedby tiny been used ithas generally been dilutedwith about unequal quantity of water, to form :1 pm cent,

or weaker, solution, and thearno'unt of such sov valyes' 136 sud i? tothe bottoms of tan-its 36 and process many advantagm are secured by alsoffooting the cleaning by my process. Among such advantages, forinstance, ore the fact that the cleaning by my process heats the .wellbore in the producing formation and the metal parts of the well, therebyrendering unnecessary the-preheating which woulcLbe required if the wellhad been cleaned by other means, the fact that no changes. need be madein the equipment and the greatssving in time;

Under the methods of .a-cidat-ion heretofore used, the smountpf acidvaries greatly, and the amount used is largely a matter of judgment,

basednp'on consideration-of the results obtained in adjacent or similar.wr-ll-s, laboratory testsupon samples of the formation, the depth ofthe well,

the thickness of the formation, and the-results it ls-desired to obtain.When muri'atlc aci-d has luti-on used has-varied from -5G0 gallons to20,000

gallons. In general, in carrying out my invention, I prefer to usecommercial muri-atlc acid without dilution, and have found that aboutone half as much ncid, that is, one fourth as many gallons as would beindicntedni'or onlyparticularv well according to the previous methods,gives a much improved result.

For carrying out the process of my invention in both cleaning andocidizing an old well 01 average type, typical apparatus would be used.

such as is shoym in the accompanying druwings.

As shown therein, the casing H is provided with a casing head l2, inwhich tubing 13 is secured.

Late-rally extending pipes it'ind ii are connected to the tubing, andsimilar pipes l6 rind H are connected to the casing head, each fittedwith a valve, i8, i9, 20 and Zlfrcspectively, pipe l4 being connected topipe 15, and pipe 15. being connected to pipe H, respectively-,beyondthe valves, preferably through T-joints having bull plugs 22- sndtherein, respectively, which installation is usual, and commonly knownas a Christmastree connection, Achoke valve 24 is usually provided inthe tubing i3, and a. pressure indicatnr 25 is suitably connected to thetubing. The pipe is connected to separator '25, as shown, or to storagetanks, as desired. All of such inst-aiintion is that usually in aproducing Well.

The added equipment preferably carried on s truck,-so as to be readilyportable, and comprises a power means 2? drivin a compressor 2-8, fromwhich flow line 25! leads through a meter 3:), a. reservoir tank 3!. to.nhsorb pulsationsf equipped; with a pressure indicator 32, and througha. valve 33 to .a heater 3'4; To the flow line 28, between the 2ml; 3!and the valve '33, there is connected a pipe 35 which is-branched toconnect to the tops of water bani: 35 andtreatznent liquid tank 31,through valves 38 and 3-9, respectively. The tanks are equipped withpressure indicators and 1!, respectively, and,

with valved inlets 32 and =33, respectively. An atomizeri i connected-inthe flow line 29 between the valve Sill and the heater 35, to a toinizeinto the new line either loater or treatment liquid, as

desired, such atomizer being fed tinjough a pipe 45 which is branchedand connected through 31, respectively. The heater 5% may be of anysuitable construction and is connected by pipe t8 gthrough a thermometeri9 to pipes M and 16, so

as to feed to the tubing or casing or both, as desired.-

In the case of a well equipped for pumping, the I pumping equipment isremoved from position to permit free accx'ss from the-tubing to thebottom of the well; In'sny case, proper connection is made so that, whenthe valves 18, l9,'2fl and 2] are closed, the top oi both the cussingand the tubing, rather than through the casing, thereby,

minimizing the loss of heat.

As a preliminary step, the producing formation sdjscent the bottom ofthe well bore is heated by circulating into the tubing, through valveis, to the bottom of the well and then back up through the casing, aboutthe -i;ubing, land through vslye 2i toa-tmosphere. a gaseous heat- ,ingmedium at the rate or about 10,000-011. it. an hour, end at atemperature of, err-exceeding, 250 F. The gas not only contacts with theface of the producing formation but bubbles up-- through, and hosts andagitates,'the fluid which generally is present in the bottom '0! thewell, and through the ii-uid in the casing it there is any presenttherein, and lends both to melt paraffin or asphalt and to cause it tobe again dissolved in the oil. This circulation is continued for aboutan hour under normal conditions, but would be maintained ior a muchlonger per-lodi! the well is deeper than average, or ii it is be lievedthat the paraiiln or similar deposits are particularly heavy. When thetemperature of the gas escaping at the top of the casing has reachedapproximately the temperature of that initially entering the top'ot thetubing, and

when likewise suflicient time has elapsed to war-..

rant the conclusion that the metalparts of the well and the face of theproducing Iorrnation.

have been cleaned, and that the perefiinend similar substances have beenmelted'or dissolved, the preheating period is considered to be com-'plete, and Valve 2! is closed. The gas used as a heating medium ispreferably natural gas-but in many localities natural gas is notavailable and air has been used frequently and satisfactorily, it beingusually advisable to use a. slightly greater quantity or air than ornatural gas. l

With only valve (3 open, the flow of the compressed gaseous heatingmedium is continued, to build up the pressure in the entire well to a.point exceeding the rock pressure of the producing iormetion, in orderto drive allot the fluid out 01 v the bore at the bottom ofthe'well andback into the producing formation. It will be appreciated that, undersome conditions in which the oil level is at a considerable distanceabove the bottom, the pressure applied through the tubing will holdsuspended between the tubing end casing a column of oil which,thersrore, will not be forced back into the iormation,'but all of thefluid thzit is in the bore will be forced therefrom bsciz'into producingformation. During this period the pressure rises gradually and finallybecomes practically stationary, at a pressure which is balanced by apressure equal to the rock pressure of the well plus the pressurenecessary to force the fluid through the pores of the formation. Ofcourse, 'it will be realized that withsorne producing formations, suchas "gravel wash" formations or cavernous iormationsit isimpossible tobuild up any material pressure, in

which case determination of how longto continue the attempt. to do so ismerely a matter of judgment.

YVhen the indicator 25 no longer shows a rise of pressure, carbontetrachloride, casinghcad gasoline, naphtha, benzine, kerosene, gas oil,or any other treatment liquid capable of-dissolving paraffln or asphalt,depending upon the exist- 'ing conditions and needs, is atomized intofiow line 29, being forced into the jet in the atomizer 40 through pipe%5, byop'ening valve M. It will be appreciated that the Surface of theliquid in tanks 36 or 37 will have been subjected to a.

high pressure- For instance, after loading, a pressure. usuallyabout-500 per square inch, is applied by closing valve 33 and openingyelve 38 or 39, respectively. It will likew se be listing in the flowline, to effect atomization. Usually, therateoi atomization-is about 100gal- Jons of llquidertorniz-ed into about 10,000 cubic feet 0! gas perhour. The rate atwhich the treatment liquid-- is atomized may. be muchhighor when the operator is warrentedin believing that it is readilypermeating the formation, but, in general, it is believed that morethorough and more extended cleaning is cfleciaed by a given amountoitreatmen't liquid if it is applied slowly during a more extendedperiod. provided, 01

course, that the rate is always bigh enough to insi' re proper heatingof the face 01' the forma-' sufficient to obtain the results expected ina produci'ng' formation of sandy lime only 5 feet thick,

the well being only 330 feet deep. On the other hand, in a badly cloggedwell 3200 feet deep in a, producing format-ion of hard sandy lime 70feet thick, 2-50 gallons of casin'g'he'nd gasoline was applied in 5hours, end such treatment was effective, but it, is believed that 150gallons would 1 have been insufficient to remove the pnrafiin.

By the time the well has been thus preheated.

and thus cleaned in a manner which further heats it under pressure, asdescribed, the cleaning vapor has been forced into the formation to aconsiderable distance from the bottom'of the well bore, thereby bothinc-reusing the porosity and permeability of such portion of the.iorm-a- .tio-n, and heating 9. materielyolume of the formatio'n, sothat, for a considerable distance from the bore, the particles of theformation will be at the temperature of condensation of the liquid used,or a higher temperature.

After the desired amount of cleaning liquid has been applied, the acidtreatment is begun, by placing in the tank 3'! 9. charge of acid asdesired, and-applying to the surface thereof a pressure, usually about500 pounds per square. inch, but. in any case materially greater thanthe pressure inthe flow line, as described hereterms, and then againopening the valve 41.

It will be understood that, in the interim, which usually is only'e. fewminutes, the flow of the gaseous medium is continued without any reduction oi pressure;

The acid is, inmost cases, preferably applied in charges or'incre'zne-nts, usually-four, the num ber being 'much greater if anunusually large, quantity of acid is to be used. The periods duringwhich such charges are applied are altermated with periods, ususlly oiabout the same duration, during which the flow of the hot compressedgaseous medium is continued. At the beginning of, or sometimesthroughout each of, such intermediate periods it has been in most casesmy practice to atom-ize into the compressed gaseous mediuma. charge ofwater from tank 38, by opening valve 08, in order to "Wash" the insideo'i-the tubing by dissolving and decreasing the corrosive effect of, theacid yepor thereon,

and to provide a medium for dissolving the cal-' cium chloride and otheproducts of reaction.

Such 'periodsof introducing acid and periods of introducing thecompressed gaseous heating medium are continued alternately untilthe-(le sired amount of acid has been applied.

At the beginning oi. each period or applying the acid vapor.

it to escape prematurely, ally is extended for two hours or more.

an acid charge, the pressure declines rapidly, sometimes to zero, whichis an indication that the action of the acid uponthe forms.-

t-io'n has opened up the pores thereof and permitted expansion into ,agreater volume 01 the formation.

After the desired acid charge has been intro duced, the flow of theheated compressed gaseous medium is continued without interruption coforce the acid vapor farther back into the formation and heat suchextended horizons of the formation in preparation for another acidcharge. During such'altcruate period, as the acid becomes spent, thepressure usually rises slowly. but it is not necessary, and in fact itis in some cases impossible within a. reasonable time, to build thepressure up to that existing when the acid was first introduced Under'most'co'nditions, I have made the intermittent periods of about thesame duration as the periods of introducing acid, but they may vaporwhich have'condensed'within the formation.

but are not'entirely spent, andto heat the formation as or as possiblefrom the well bore to a temperature above the point of condensation 01 Afurther purpose as stak d heretofore, is to afford a means of convey ngwater in the formof steam to the inner surface of the tubing to lessenthe corrosive action of the acid thereon, and to insure that saltsresulting from the act-ion of the acid will be dissolved.

After the final charge .0: acid has been loner .duced, the introductionof the heated-compressed gaseous medium is continued for the samepurposes as described with reference to the intermediate periods, but asa. rule the application period, after the final acid charge, is greatlyextended, in order to build up the pressure, 11 possible, to at leastthe pressure that had been attained before the acid was applied. In anycase, the period would be extended long enough to insure that the acidhas become spent.- The bottom of the well 'bore'will carry along withthem particles of water containing reaction products in solutiontherein, and particles ofoil, p2 .afilnor sand, and similar'bodles. Toobtain this flushing action is it of course desirable that the pressurebe as high as possible, so that the action will originate as far aspossible from the bore and will be as violent as possible, to vemove asvmany particles as possible and increase the tendency to form openchannels in the formation and leading'to the bore, and itis ofcourse-preferable that none of the acid bewasted by allowing This finalperiod usu- The pressure is then suddenly released by closing valve l8,and opening valve IE, or both valve l9 and valve 2|. It willlie-appreciated that, in the case ofa flowing well, it would bepreferable-to open only'valve 19, while in the case of a suddenly aspossible.

45 tion,

' "memes pum ing well," that is, one um it has been necessary to pump,it someti-mesmay be desirable.

to open valves lQZa'nd 2.,-lnorder to release the pressure inboth thetubing and the casing as The gases blown ofl escape and any liquidmixture of oil,. salt water, -etc., is run into the slush pit until thewell has purged itself and mellow is suitable fol-use. Likewise, in thecase '0! a pumping well, the

10 undesirable liquid mixture is pumped out and discarded, or ifdesired, such undesirable mixture may beiernoved by bailing or swabbing,orsim-- 1-5 cleaned, the acidizing treatment beingconsidered'onnecessary orundeslra'ble for any reason, the steps .forcleaning are carried out exactly as hereinbefore described, and the wellis placed back in production as above described, except that in'suchcase it is usually preferable that the well be closedin and kept sealeduntil the pressure is substantially normal before placing the well "backin production." In this reduction of pressure to normal does not occurin a reasonable length of time, the pressure should be rethat, under thepressure applied, the vapor is unilormly distributed throughout theentire depth of the formation at the bottom of the well and attacks thewall uniformly regardless of the size and shapeof the opening that mayexist,

so thatthe effect will'tend to be that shown in Fig. 1. On the otherhand, if the treatment liquid is durnped into the well in liquid form,

and pressure is applied to the liquid, such pressure tends to force theliquid away from the bore-nearil1e-bottpm of the formation because somegreater pressure there, and because if the liquid can there enter theformation all of it may be fed into such part, of the lormation andneverr'e-ach the higher portions of the iorma- If the well has had aprevlousacidizing tre'atment,.and as a result of such treatment, or forany other reason, there exists an opening of cor"ierable size at thebottom of thewell, such as shown in Fig. 1, itwill be quite evident thata liquid acid charge of less volume than such .opening could not.possibly reach-the upper parts purpose of this period of application ofgas under of the formation, while a char-go applied in vapor form wouldreach all of the surface of such an opening regardless of its size, andwould attack all of such 'suriaceuniiormly.

It mu be understood that, "while it is pref-erable to atomize thetreatment liquid into the flowing stream of compressed gaseous mediumand heatthe mixture, such exact arrangement of 50 the parts is notessential and that the compressed ,erable, for the reasons stated, totreat the well' through the tubing, rather than through the casing, itwill be understood that in shallow wells it would be possible to applythe treatment through the casing, particularly when the-pressurenecessary is low and when conditions are,

such that the loss or heat through the easi-ng could be overcome.

- It will be apparent that by the application of any treatment liquid asherein described, so that it reaclislhe preheated formation in vaporform. H

its 'ell'ecti'veness will be greatly enhanced over that of the samesubstance in liquid form, not only because it can be tore-ed fartherinto the iorxnation, by the same pressure, .than a. liquid could beforced, thus greatly increasing the volume of the format-ion which wouldbe rendered permeable and porous, but also because such preheat theproducing formation adjacent the bottom of the well, and thenintroducing into the top of the well a gas comprisingin vapor form atreatment liquid which is capable of attacking the obstructions to flowand which is liquid at normal temperatures, such gas being at a.pressure exceeding the roe-k pressure of the producing formation and ata temperature above the point of condensation or such treatment liquidat the existing pressure.

2. The method of treating a well to remove obstructions to flow, whichcomprises introducing into the welladjacent its top a heated gas at a.pressure materially exceeding the rock pressure of the producingformation to force from the bottom of the well bore back into theproducing formation any fluid present in the bottom of the V well boreand to preheat aportion of the producing formation adjacent the bottomof the well bore, and then introducing into the well adjacent agentcapable of reacting with particles of the producing iorrnatlon and at apressure-exceeding the rock pressure or the prod'u'cinpier-motion.

4. The method of treating a well to, remove obstructions-to flow;whichcomprises introducing into the well a heated, compressed gas-for a.

period of sufficient duration to buildup "a pres sure'exceedi'ng ther'cteic pressure of-the producing formation, introducinginto the wellduring asu'cceedihg'period a heated compressed gaseous .rnedium. capableof dissolving paraffin, and introducing into the well during asucceed-lug period a heahd gaseous medium'co-ntaining an gold in vaporform and at a. pressure exceeding the ro'ck'pressure-oi the producingformation.

5. The method of treating a well to remove obstructions to flow, whichcomprises introducing into the well a heated, compressed gas for a'period of suiiicient duration to heat a portion of the producingformation, introducing into the well during a succeeding period aheated, compressed gaseous medium capable of dissolving paraffin, andthen introducing into the well dur ing alternate periods aheatedcompressed gaseous medium containing anncid in vaporiorm and aheated,'gaseo-us medium substantially tree of acid at a pressureexceeding -the r'oci'; pressure of the roducing formation.

6. The method of treating a well to remove obstructions to flow, whichcomprises introducing into the well a "heated, compressed gas for aeriod of vsuificient duration'to heat a portion of the producingformation, introducing intothe well during a succeeding period a heated,compressed gaseous niedi-um capable of dissolving' pa-rali'in andthereby building up .a pressure exceeding the rock pressure of theprOr-iucing foriis-top a. heated, compressed mixture o'f's. gas,

and-the vapor of a treatment liquid which is capebie of changing thec'i-ieracteristlcs of the ob stmrctions to flow end which is liquid atnormal temperature and .pressiu-e, such mixture being introduced at atemperature exceeding the tem- :pern'ture of condensetionpf suchtreatment liquid at "the rock pressure or the Iaroducing formatiolL 3.The method or treating a well. to remove obstructions to. flow, whichcomprises introducing into the well adl-ace'nt its top a heated,compressed gas for aperiod of sufiicient duration to heat-e portion oftl'iesprod-ucing format-ion, introducing into the well during asucceeding period a heated gaseous medium capable ofdissolving parsfiinand at a pressure exceeding the rock pressune of' the producingformation, and intro? ducing during a. succeeding period a heated,

gaseous medium containing in vapor form 'a rethe existing pressure.

motion, and introducing into thew'el-l during sueceeding alternateperiods a heated, gaseous medium containing an scidin vapor formcompressed to a ressure exceeding the rock pressure or the producingformation and such hes-ted, compressed gaseous medium, substantiallyfree from acid and containing steam during at least a part of suchperiod.

'I. The method of treating a well to remove obstructions to now, whichcomprises com-pressing a gaseousmedium to a pressure exceeding the rockpressure of the producing formation and; heating it, maintaining a flowof :such' heated compressed gasem-is rnedium into the well,

and intermittently mirdng' with the stream of gaseous. medium atreatment V liquid in vapor form, the temperature of sold gaseous mediumbeing maintained at a point above the temperature oi condensation ofsuch treatment liquid at EOSEPH S. NQRMAND.

